The present invention relates to a system for supporting an architectural element, and more particularly, to a homeostatic system for supporting an architectural element such that the supporting structure resists unexpected, infrequent shocks such as might be encountered during an earthquake or other disaster and isolates the architectural element from variations in the level or stability of the surface on which the supporting structure rests.
Buildings and other architectural structures may be built in locations where such structures are susceptible to damage from seismic shocks. Conventional construction methods frequently result in essentially rigid structures, i.e., structures that do not yield appreciably on the application of an external force. When an external force is applied to such a rigid structure, a variety of tensile, compressive and bending forces may be created within the structure. If the external force is sufficiently high, the structure may fail, resulting in damage to the structure and the risk of harm to persons and property in and around the structure. To reduce the risk of such occurrences, existing methods for constructing rigid structures in such locations frequently call for overdesign of at least some portions of these structures.
Methods for constructing rigid structures may include the use of devices, such as rubber bearings containing a core of lead to absorb heat, to provide some degree of seismic isolation to these structures. These isolating devices have several known disadvantages. The devices depend on the interaction of specialized materials, some of which tend to deteriorate over time, resulting in decreased protective capacity or increased expenses associated with periodic replacement. Known bearings also are unlikely to be capable of responding to the magnitude of the displacement associated with a severe seismic event. Bearings that lack sufficient shock-absorbing capability may exaggerate rather than minimize the effects of seismic shock.
Other known construction methods result in flexible structures that are capable of yielding to an external force. However, because these structures generally lack means for effectively dissipating energy, they tend to store the energy associated with application of an external force in a spring-like manner, resulting in undesirable oscillation of the structures. Such oscillation may disrupt use of a flexible structure, for example, during high wind conditions. Under more extreme conditions, oscillation of a flexible structure may result in damage to the structure and the risk of harm to persons and property, as described above.
Buildings and other architectural structures also may be built in locations where soil or other surface conditions are not conducive to placement of the structures directly upon the ground. In such cases, the buildings may be constructed upon a platform or similar structure supported above the ground. Conventional methods for supporting structures above a surface have the same shortcomings as the above-described building construction methods. In addition, these conventional methods generally are ineffective in isolating the structures from variations in the level or stability of the surface on which the supporting structure rests. For example, erosion or settling of loosely packed soils may alter the level of a portion of the surface on which the supporting structure rests. Variations in the water table, or the seasonal freezing and thawing of the soil in extremely cold regions, including permafrost soil, may affect the consistency of the surface underlying a structure. Surface changes such as these may be transmitted to a conventional supporting structure, resulting in damage to the structure placed thereon and the risk of harm to persons and property, as described above.
The system of the present invention may be practiced using simple construction techniques and materials, requires minimal maintenance, and is capable of reacting to displacements of a large magnitude. The present invention provides a system for supporting an architectural element on a structure whose elements are in or tending toward a relatively stable state of equilibrium. "Homeostasis" is defined as "a relatively stable state of equilibrium or a tendency toward such a state between the different but interdependent elements or groups of elements of an organism or group." (Webster's New Collegiate Dictionary, G. & C. Merriam Co., 1976.) Hence the system of the present invention may be referred to as a homeostatic system.
The present invention provides an apparatus for supporting an architectural element upon a structure. The supporting structure includes a pair of laterally spaced apart fixed bearing members arranged on a surface beneath or adjacent to a site for an architectural element. Each bearing member may be associated with a bearing surface for engaging an elongated member. An elongated member may be arranged with a midportion extending between a pair of bearing members and end portions extending longitudinally beyond the pair of bearing members. A bearing surface may engage an elongated member at a distance spaced inwardly from one of the ends of the elongated member. An architectural element, which may comprise a base upon which one or more buildings or other architectural structures may be disposed, a building or other architectural structure, or a portion of a building or other architectural structure, may be placed in association with the elongated member.
The corresponding method includes arranging a pair of laterally spaced apart fixed bearing members on a surface beneath or adjacent to a site for an architectural element and supporting an elongated member on a bearing surface of each of the bearing members in the manner described above. An architectural element may be placed in association with the elongated member.
The elongated member of the system is capable of both supporting at least a portion of an architectural element and bending in proportion to the magnitude of a load applied to its midportion intermediate the end portions. The system of the present invention establishes an equilibrium state between the bending elongated member and the weight of the architectural element.
Beginning from a state in which an elongated member is in equilibrium with an associated architectural element, an additional load applied intermediate the ends of the elongated member causes the midportion of the elongated member to bend from a first equilibrium position an amount proportional to the magnitude of the additional load and assume a second, more downwardly bowed position. The ends of the elongated members slide against the bearing surfaces a distance also proportional to the magnitude of the additional load as the midportion bows downwardly. The movement of the elongated member establishes a new equilibrium state between the bending elongated member and the total applied load, which consists of the weight of the architectural element and the additional load. When the additional load is removed, the midportion tends to unbow, returning to substantially the same position as its original equilibrium position. The ends of the elongated member slide a corresponding distance in the opposite direction, also returning to substantially the same positions as their original equilibrium positions. The midportion of the elongated member bends and the ends of the elongated members slide in a similar manner in response to a force applied upwardly against the bottom of a bowed elongated member or in response to a force applied against any of the bearing members.
The bending and sliding of the elongated member in response to changes in the load supported by the structure may perform shock and energy absorbing functions as the elongated member engages the bearing surfaces. The absorbed energy is dissipated primarily in the form of heat generated by the frictional contact between the elongated member and the bearing surfaces. Preferably, the elongated member engages the bearing surfaces during bending under load at a preferred angle, i.e., an angle within the range of about 25 to about 50 degrees from a vertical axis of support for the structure, recognizing that angles outside this range also will achieve the desired result and are included in the present invention.